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Re: Compression and 87 Octane

To: klarsen@inreach.com (Kendall Larsen)
Subject: Re: Compression and 87 Octane
From: tr6taylor@webtv.net (Sally or Dick Taylor)
Date: Wed, 26 Jul 2000 23:15:12 -0700 (PDT)
Kendall---The only "engine management system" in the TR6 is at the end
of your right foot. This is to mean that while other (more modern)
engines can run, in most circumstances, with 87 octane and a 9.0:1
compression ratio, the TR6 will ping, unless driven with little load on
the engine.  I don't want to repeat here the quieting affect fuel inj.
and engine management thru computor control can have on this pinging
phenomenon, other than to say that it does.

Raising the comp. ratio up 1.5 points will produce maybe 10 more h.p.
I'm not sure whether you would feel this in the seat of your pants or
not. It would be the equivalent of about one or two car lengths from 0
to 60, everything else being equal.  If the engine pings, you can work
out a combination of retarding the spark, and increasing the octane of
the fuel, till this ping goes away. You may not hear it except when
pulling a grade, or low in the rpm band.

Finally, do not be concerned about any "future boring out of the
cylinders." You cannot bore out a TR block enough to effect the
compression ratio. Briefly, this is the area between the top of the
piston and the volume inside the head, as determined by the stroke of
the crankshaft. Bore size really doesn't count for much here.

Dick Taylor
'73


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